The structure is a souterrain, an early medieval underground passage or chamber built without mortar from carefully stacked dry stone, typically used for storage or refuge. What makes this particular example quietly arresting is its plan: roughly Z-shaped, it changes direction not once but twice, the second exit now blocked by stone. Someone, at some point, decided to seal it off.

The site sits within a cluster of remains that speak to a longer occupation of this hillside. The townland name Cill Chúile almost certainly derives from an early church here, and local tradition identifies the surrounding ground as a burial place. The souterrain itself was documented in detail by J. Cuppage as part of the Corca Dhuibhne archaeological survey published in 1986. Cuppage recorded the entrance on the east side of a dividing wall, reached by a sloping ramp down to a first passage extending west-south-west for just over one and a half metres, roofed by three stone slabs and barely a metre high. From the western end, a lintelled opening barely forty-two centimetres wide leads into a second passage running south-south-east for just over three metres before curving south-west for a further one and a half metres. There, a second lintelled doorway, similar in construction to the first, has been blocked. The whole arrangement is compact, deliberate, and built to last.

The careful detailing of the lintelled openings is worth pausing over. In each case, upright slabs project slightly out from the passage walls to define the threshold, and the lintel sits below the roof level, leaving a gap above it. This is a recurring feature in Irish souterrains and is thought to have made the passage easier to defend or close off, a small but telling detail in a structure that was plainly built with concealment or security in mind.